Welcome aboard to a fellow Pacific Northwesterner!!

If you're gonna handload, no sense in the 450M, it's not available in rifle form anyway, just as an accessory barrel, just go for the 45-70 or 500 in a rifle and get the other barrel, or heck, get both of the others, just decide whatcha want first!!

The 450M only has an advantage if you're hindered by factory ammo, handloaded they're ballistic twins in levergun data, get into ruger data and the 45-70 walks away.

If you get the 500 and stick with factory ammo, better get a second job, or expedite the handloading process, that stuff ain't cheap!!

If you want a reasonable working man's scope for the any of them, see the
45-70 scope link in the FAQs and Help sticky,(spend some time in there, lots of your quesitons will be answered) lots of choices, the 1½-4½x32 Bushnell Banner is at the head of the pack for a working man's scope, reasonably priced and well suited for the task.
Another scope is the Nikon Prostaff 2-7x32, I have one on my 500 S&W, great scope for a bit more than the Banner.
Tim